Cavity resonator structure for klystrons



Sept. 21, 1965 F. L. SALISBURY CAVITY RESONATOR STRUCTURE FOR KLYSTRONSOriginal Filed May 2. 1960 'P/E. Z

IN VEN TOR. E'eMeWZ'CX L SZxZz'sZz/r) lay United States Patent 3,207,942CAVITY RESONATOR STRUCTURE FGR KLYSTRQNS Frederick L. Salisbury, LosAltos, Calif, assignor to Varian Associates, Palo Alto, Calif., acorpnration of California Original application May 2, 1960, Ser. No.26,249, new Patent No. 3,097,324, dated July 9, 1963. Divided and thisapplication Apr. 24, 1963, Ser. No. 275,419 1 Claim. (Cl. 313-337) Thisapplication is a divisional of co-pending U.S. application Serial No.26,249, by Frederick L. Salisbury, filed May 2, 1960, now titled, CavityResonator Structure for Klystrons, which has matured into US. Patent No.3,097,324.

This invention relates in general to high frequency electron emissivedevices and method of making same.

In electron discharge devices such as klystron tubes which have had acentral body portion with an axial bore therein subdividedlongitudinally by a plurality of cavity resonator partitions in the formof headers supporting drift tubes, the headers have been brazed atprecise locations within the bore to provide specific gap spacingsbetween the drift tubes supported by the headers. In the past, theseheaders were tightly held on shoulders within the bore of the tube priorto brazing, or in some instances spacers were provided in the gapsbetween adjacent drift tubes. In the latter case these spacers, ofcourse, had to be removed from the tube after the brazing operation hadtaken place. These prior art assembly methods depended upon maintainingclose tolerances in forming the bore and the headers so that the headerscould be slideably positioned within the bore and held in axialalignment until the brazing operation could be completed.

Furthermore, in tubes of this nature it is necessary to provide anaccurately aligned longitudinally positioned cathode assembly forproducing the electron beam that is to pass through the tube. odes beeasily assembled and accurately adjusted for the desired cathode-anodespacing regardless of discrepancies in the size of other parts of thetube. In many previous tubes the entire cathode assembly was assembledin one operation whereby allowances for variations in the dimensions ofthe tube could not readily be made.

The object of the present invention is to provide a novel electrondischarge device and method for making the same whereby a rugged tubecan be more easily and economically produced while keeping within closetolerances.

One feature of the present invention is the provision of a novelelectron discharge device constructed from a bare minimum of separatecomponents assembled in a rugged unitary device capable of meeting rigidrequirements for reproducing specific electrical requirements in spiteof mechanical variations in certain portions of the tube.

Another feature of the present invention is the provision of a novelcathode assembly including a stem-heater assembly and acathode-electrode assembly which can be slideably adjusted and thenfixed together to provide the desired cathode-anode spacing therebycompensating for any changes in the sizes or positions of other membersof the tube.

Still another feature of the present invention is the provision of anovel method for forming the cathode assembly of an electron dischargedevice including the steps of forming a stem assembly with the heaterfilament thereon, forming a cathode and focus electrode assembly,slideably positioning the cathode-electrode assembly on the stemassembly for the desired cathode-anode spacing for the device, fixedlysecuring the cathode-electrode assembly to the stem assembly andmounting the stem assembly on the end of the device.

It is desirable that these cath-' 3,207,942 Patented Sept. 21, 1965Other features and advantages of the present invention will become moreapparent on a perusal of the following specification taken in connectionwith accompanying drawings wherein:

FIG. 1 is a longitudinal cross-section view, partially in elevation, ofa klystron tube utilizing the features of the present invention,

FIG. 2 is an enlarged side cross-section view of the stem-heaterassembly and the cathode-electrode assembly of the klystron tube shownin FIG. 1 and showing in phantom the manner in which these assembliesare put together,

FIG. 3 is a side cross-section view of the main body portion of aklystron tube showing the novel manner in which the annular headers arepositioned within the bore of the main body portion,

FIG. 4 is a side cross-section view of a portion of the body of anelectron discharge device utilizing the features of the presentinvention, and

FIG. 5 is a side cross-section view of a portion of the body of anotherelectron discharge device utilizing features of the present invention.

Referring now to FIGS. 1 through 3 of the drawing, a klystron tubeutilizing features of the present invention includes a central bodyportion 11 which is made from a unitary metallic block having amultidiarneter longitudinal bore 12 extending therethrough. A metallichollow cylindrical drift tube 13 of a material with a relatively lowcoefficient of expansion such as steel and having circular resonatorgrids 14 and 15 on the ends thereof is positioned within thelongitudinal bore 12 by an outwardly extending annular header 16. TheWalls of the drift tube 13 are parallel to the axis of the electron beampassing through the central body portion 11 of the tube. Fixedlysecured, as by brazing, within one end of the longitudinal bore 12 ofthe central body portion 11 having an enlarged diameter is an annularanode structure 17 as of, for example, copper having a resonator grid 18positioned in the aperture therethrough, and within the other end of thecentral body portion 11 is an annular header 19 as of, for example,copper and with a resonator grid 20 positioned in the aperturetherethrough. Within the central body portion 11, the annular anodestructure 17 and the annular header 16 on the drift tube 13 serve asresonator partitions and define a re-entrant first cavity resonator 21;the header 16 on the drift tube 13 and the header 19 serve as resonatorpartitions and define a reentrant second cavity resonator 22. The header16 on the drift tube 13 is provided with an aperture 23 therethrough forcoupling the first and second cavity resonators 21 and 22 together. Amilled opening 24 in the side wall of the central body portion 11provides access to the second cavity resonator 22 for couplingoscillatory energy out of the tube.

The drift tube 13 which is made of a metal with a relatively lowcoeflicient of expansion prevents the gaps between the grids 14 and 18and grids 15 and 20 from changing an appreciable amount when theklystron tube heats up.

The anode structure 17 and the headers 16 and 19 are positioned withinthe bore 12 of central body portion 11 by first providing raisedportions such as knurls 25a, 25b and 250 respectively (see FIG. 3),encircling the wall of the bore 12 of central body portion 11 at thepositions at which these members are to be fixed. The surface surrounding the bore 12 of the central body portion 11 is then copperplated. The annular header 16 which is of smaller diameter then thatportion of the bore 12 at which the anode structure 17 is positioned ispressed into place on its knurl 25b through the anode end of the centralbody portion 11 clearing the knurl 25a. Then the anode structure 17 ispressed into place on its knurl 25a a and the header 19 is pressed intoposition on its knurl 250 at the other end of the tube. In this mannerthe headers which constitute the cavity resonator partitions can beaccurately positioned within the longitudinal bore and held thereinuntil they can be more tightly secured to the tube body, as by brazing,if that is desired. The assembled central body portion may then beplaced in a brazing oven to fixedly secure the members in place withinthe longitudinal bore 12, as by, for example, the use of rings ofbrazing material positioned around the edges of the partitions at thetime of insertion of the partitions into the body.

The raised portions may be provided by knurling or embossing the surfacesurrounding the bore 12 so long as the surface is raised up into thebore such as a ridge or a series of ridges, a straight knurl or adiamond knurl, etc. Hereafter, in the specification and claims the wordknurl will be used to indicate any such raised portion.

Although this method of assembly is illustrated as applied to a tubewith only two cavity resonators it can be seen that this feature of thepresent invention can be used to assemble a tube with any number ofcavity resonators (see FIG. 4). In a tube with, for example, fivesuccessive cavity resonators A, B, C, D and E formed by successiveresonator partitions a, b, c, d, e and f, the longitudinal bore isprovided with a stepped diameter, the narrowest portion of the surfacesurrounding the bore being substantially midway thereof and forming thecircumferential wall for cavity resonators B, C and D. The diameter ofthe surface surrounding the bore is stepped outwardly in two placestoward each end thereof to form the circumferential wall for cavityresonator A at one end of the bore and cavity resonator E at theopposite end of the bore. Knurls are provided at the desired locationsfor the resonator partitions a, b, c, d, e and f, and then partitions a,b and c are slideably inserted into their proper positions from one endof the bore and partitions d, e and f are slidably inserted into theirproper position from the other end of the bore. Because of the steppeddiameter of the bore each partition is of such a diameter as to clearall the knurls for larger diameter partitions. To facilitateconstruction of the tube equal steps in the diameter of the bore areused toward each end thereof, and these steps are provided at thedesired location for the inner edge of a partition so that certainpartitions are accurately positioned within the bore by being pressedagainst the steps in the diameter of the bore.

Referring to FIG. 5 as an alternative embodiment of this presentinvention a tube with any number of cavity resonators can be assembledby positioning cavity resonator partitions on knurls within a bore ofuniform diameter. Successive cavity resonators A, B, C and D are formedalong the length of the bore by successive partitions a, b, c, d and e.A knurl is provided on the surface of the bore adjacent the midportionthereof and the resonator partition c is slideably inserted into one endof the bore and positioned on this knurl. The knurls for walls b and dare then formed and associated walls b' and d then inserted thereonafter which two additional knurls are formed and associated walls a ande secured thereon. In this embodiment of the present invention theknurls could be properly spaced along the length of the bore by placinga guide extension on the end of the knurling tool so that eachsuccessive knurl will be made at a desired distance from an existingpartition within the bore. Obviously the two central-most partitionscould be inserted into the bore and onto knurls at the same time fromopposite ends of the bore. It should be noted that the knurls on thewall of the bore need not extend in a complete closed circle around thebore to perform their functions but may, for example, include two ormore segments of a circle.

Fixedly secured, as by brazing, within an annular flange 26 on the endof the central body portion 11 adjacent the anode structure 17 is hollowcylinder 27 which supports a beam generating assembly 28. In order toassure proper alignment and spacing of the beam generating assembly 28,it is constructed from two sub-assemblies, a stemheater assembly 29 anda cathode-electrode assembly 31.

In the stem-heater assembly 29 an insulator disc 32 such as ceramicforms the end of the tube and is provided with an annular projection 33projecting axially into the tube and covered with a disc-shaped sputtershield 34 which is dished to project into the space surrounded by theannular projection 33. Mounted on the sputter shield 34 is anopen-ended, cup-shaped heat shield 35. Heater and cathode leads 36project through and are sealed within apertures in the insulator disc 32by means of brazing washers 37, and the leads 36 pass through aperturesin the sputter shield 34. One end of an openended, cup'shaped stemassembly support member 38 is fixedly secured to the side of the disc 32facing into the tube outside the annular projection 33, and the otherend is adapted to support the stem-heater assembly 29 from the end ofthe hollow cylinder 27. All the parts of this stem-heater assembly 29are held together in a jig and simultaneously brazed together in thebrazing furnace.

Connecting tabs 39 are added connecting two of the leads 36 to the heatshield 35 thereby providing electrical connection to thecathode-electrode assembly 31 to be mounted on the stem-heater assembly29. A spiral heater filament 40 projecting axially into the tube withinthe heat shield 35 is then connected to the remaining lead 36.

The cathode-electrode assembly 31 includes cathode button 41 connected,as by spot welding, to an annular flange on one end of a hollow heaterhousing support cylinder 42. The other end of the support cylinder 42 isaxially supported within a hollow cylindrical support sleeve 43 by meansof an annular sleeve adapter 44. The support cylinder 42, the supportsleeve 43 and the sleeve adapter 44 are held in a jig and brazedtogether in a brazing furnace. An open-ended, cup-shaped focus electrode45 with a stepped diameter fits within and is supported at the step inits diameter on the forward end of the support sleeve 43.

The critical adjustments in the beam generating assembly 28 are axiallypositioning the cathode button 41 with respect to the central bodyportion 11 to form a beam that will pass through the entire tube andachieving the proper distance from the cathode button 41 to the anodestructure 17 to properly form the beam and to pass as much of the beamas possible through the anode structure 17.

The cathode-electrode assembly 31 is connected to the stem-heaterassembly 29 by sliding the heater housing support cylinder 42 over theheater filament 40 and sliding the support sleeve 43 within the heatshield 35. In this manner, the heater filament 40 is positioned behindthe cathode button 41 for initiating thermionic emission, and thecathode-electrode assembly is positioned axially of the stem-heaterassembly 29. With the stern assembly support member 38 positioned withinan annular flange 47 on the end of the hollow cylinder 27 the entirebeam generating assembly 28 will be positioned axially with respect tothe central body portion 11.

To position the cathode button 41 the proper distance from the anodestructure 17 before mounting the cathodeelectrode assembly 31 on thestem-heater assembly 29, the distance between the tip of the anodestructure 17 and the annular flange 47 on which the stem heater assemblywill be supported is first measured. While mounting thecathode-electrode assembly 31 on the stemheater assembly 29 theseassemblies are moved axially with respect to one another so that thedifference between the distance from the forwardmost portion of thestem-heater assembly support member 38 to the cathode button 41 and thefirst distance measured will provide the proper space between thecathode button 41 and the anode structure 17. Then, the heat shield 35and the support sleeve 43 are fixedly secured together, as byspot-welding, thereby connecting the stem-heater assembly and thecathode-electrode assembly 31. This connection can be more rigidlyfixed, as by silver brazing, to make the tube more rugged.

As an additional feature in the beam generating assembly 28, as shown inphantom in FIG. 1 the support sleeve 43 can be divided into two portionsinsulated from one another by in insulator ring 48 such as aluminaceramic whereby the focus electrode 45 can be provided with a positiveor negative bias with respect to the cathode button 41 by means of anadditional lead (not shown).

For mass production of tubes utilizing the beam generating assemblyillustrated here the stem-heater assembly 29 and the cathode-electrodeassembly 31 for every tube could be connected together with a standarddistance between the forwardmost end of the stem assembly support member38 and the cathode button 41. Then a spacer ring of selected thicknesscould be provided between the forwardmost portion of the stem assemblysupport member 38 and the annular flange 47 on the hollow cylinder 27 tocompensate for variations in the distance between the annular flanges 47and the tip of the anode structure 17 on individual tubes.

A tab 49 is attached to the outside wall of the central body portion 11for electrically grounding the tube body.

A collector assembly 50 including an annular adapter 51 of non-magneticmaterial such as steel connected to one end of a hollow cylindricalcollector 52 such as copper provided with radially outwardly extendingcool ing fins 53 is fixedly secured to the end of the central bodyportion 11 adjacent the header 19 such as by a braze between the adapter51 and the central body portion 11. An annular protective fin 54 of ahard material such as steel is fixedly secured to the other end of thecollector 52 to protect the other fins 53 from being bent out of shapedue to rough handling of the tube. An exhaust tubulation 55 closes offthe outward extending end of the collector 52 and is providedtherewithin with a milled baffle 56 which provides gas access betweenthe tube and the tip of the exhaust tubulation 55 but prevents directbombardment of the tip of the tubulation 55 by electrons travelingaxially down the tube. Since the annular adapter 51 is made ofnon-magnetic material the col lector assembly 50 is magneticallyshielded from the remainder of the tube to prevent focusing of theelectron beam within the collector assembly 50.

A waveguiding recess 57 is milled into the central body portion 11surrounding the milled opening 24, and within this recess 57 a wavepermeable window 58 such as alumina ceramic is supported in a cup-shapedwindow frame 59 vacuum-sealed to the external surface of the centralbody portion 11 within the recess 57. A waveguide output flange 60surrounds the recess 57 for coupling the tube to other microwavecomponents.

Each of the cavity resonators 21 and 22 is tuned by an identical tuningassembly 62 contained in a tuner mounting block 63 supported on the sideof the central body portion 11 opposite from the wave permeable window58. A milled opening 64 is provided in the central body portion 11 intoeach cavity resonator, and then both cavity resonators are sealed closedby a flexible tuner diaphragm 65 which is held between the central bodyportion 11 and the tuner mounting block 63. For each cavity resonator acylindrical tuner rod 66 is slideably mounted within a cylindrical borein the mounting block 63, one end of the tuner rod 66 being fixedlysecured to the tuner diaphragm 65 for moving the tuner diaphragm in andout to tune the cavity resonator. Each tuner rod 66 is provided with atransverse slot 67 thereacross, and the mounting block 63 is providedwith a large cylindrical aperture 68 communicating with the bore whichhouses the tuner rod 66, the axis of the aperture 68 being substantiallyperpendicular to the axis of the tuner rod 67 and providing access tothe transverse slot 67 in the tuner rod 66. A tuner tool which lideablyfits within the aperture 68 and is provided with an eccentric projectionon the end thereof adapted to fit within the transverse slot 67 can beused to tune each cavity resonator whereby when the tuner tool isengaged in the aperture 68, rotation of the tool will move the tunerrods 66 in and out to tune the cavities. A set screw (not shown) isprovided on the opposite side of the mounting block 63 from the aperture68 for locking the tuner rod 66 when the cavity resonators have beenproperly tuned.

The construction of the central body portion with the cavity resonatorpartitions and the beam generating assembly and the methods ofassembling these portions of the tube would be equally applicable toelectron discharge devices other than klystron tubes and utilizing aplurality of cavity resonators such as, for example, traveling wavetubes and linear accellerators using disc loaded waveguide.

Since many changes could be made in the above construction and manyapparently widely dilferent embodiments of this invention could be madewithout departing from the scope thereof, it is intended that allmatters contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:

An electron discharge device comprising a stem-heater assembly whichincludes an insulator disc adapted to close one end of the device, acup-shaped heat shield supported axially on the inner face of saidinsulator disc, heater means supported axially within said heat shieldand an axially aligned stem assembly support member positioned on saidinsulator disc surrounding said heat shield and a cathode-electrodeassembly including a hollow, cylindrical support sleeve, an annulardisc-shaped sleeve adaptor having an aperture therein and fixedlypositioned within said support sleeve, a hollow cylindrical heaterhousing positioned within the aperture through said sleeve adaptor, acathode button positioned on the end of said heater housing and anopen-ended, cup-shaped focus electrode positioned on the end of saidsupport sleeve in front of said cathode button, said support sleeve ofsaid cathode-electrode assembly being fixedly secured within said heatshield of said stem-heater assembly whereby the distance between cathodebutton and the end at which the stem-heater assembly support member issupported on the electron discharge device will leave the desireddistance between the cathode button and the anode structure of theelectron discharge device when the stemheater assembly is fixedlysecured to the end of the electron discharge device.

References Cited by the Examiner UNITED STATES PATENTS 2,018,071 10/35Kuhle et a1 315-39 2,456,861 12/48 Carter 315-5 2,644,907 7/53Drieschrnan et al. 313-249 2,655,614 10/53 Doolittle et a1 3 13-2492,965,794 12/60 Gardner et al. 315-5 JOHN W. HUCKERT, Primary Examiner.

DAVID J. GALVIN, Examiner.

